Unlike home audio equipment that is generally designed to operate in a single speaker configuration, commercial audio equipment is often designed to operate in a number of speaker configurations in order to drive speakers with a wide range of impedances. Commercial amplifiers, which can produce between 500-20,000 watts of power, are often designed to be able to drive multiple speakers in parallel or to drive single speakers (e.g. subwoofers) to high sound pressure levels. Because it is not cost effective to design a single amplifier channel that can drive every different type of load to the same power level, many commercial amplifiers are designed to operate in different modes. These modes can include using one channel to drive one or more speakers, combining the outputs of two or more amplifier channels in parallel to drive one or more speakers or connecting two or more channels to drive speaker(s) in a bridge-tied load or a combination such as a parallel bridge-tied load.
In order to reduce power loss in amplifiers, many commercial audio amplifiers use switching amplifier topologies such as class D designs. When any amplifier channels are connected in parallel, it is difficult to ensure that each channel contributes equally to current delivered to the load. To prevent this, multi-channel amplifier designs often employ special current monitoring feedback circuits that operate to ensure that the current delivered by each channel is the same. Such feedback circuits not only increase the cost of the amplifier designs but are a potential source of error if each feedback circuit in the amplifier does not operate correctly.
Another problem faced by users of commercial audio amplifiers is knowing the best way to connect their speakers to the amplifier. Many users will want to drive various combinations of speakers with different impedances. The user typically has to review tables or charts that list the current and voltage capability of an amplifier channel, the load impedance of various speakers and speaker configurations and other factors in order to determine the best way to drive their speaker loads. The user has to use this information to select a speaker configuration and then determine how to configure the amplifier and connect their speakers to the amplifier in the selected configuration.
Given these problems, there is a need for a multi-channel amplifier design that is less expensive to manufacture, can handle the current sharing problem of amplifier stages driving loads in parallel and can aid the user in determining how to best connect their speakers to the amplifier.